The present invention relates to a circular knitting machine, and more specifically to such a circular knitting machine, which enables the user to replace the top and bottom cam holders without detaching the yarn feeding unit and the knitting unit.
A regular circular knitting machine 1, as shown in FIG. 1A, is generally comprised of a yarn-feeding unit 13 at the top, a knitting unit 2 in the middle, and a fabric-receiving unit 12 at the bottom. The yarn-feeding unit 13 is supported on supports 14, comprising a suspension rack 141 adapted to hold the knitting unit 2. Please see also FIGS. from 12 through 15, a center shaft 32 is provided at the center of the suspension rack 141. A top needle plate holder 3 and a bottom needle plate holder 33 are respectively is mounted on the center shaft 32 at different elevations. The top needle plate holder 3 carries a top needle plate 31, which has horizontally radially extended needle grooves 311. The bottom needle plate holder 33 carries a bottom needle plate 3, which has vertically extended needle grooves 341 respectively aimed at the needle grooves 311 of the top needle plate 31. Top needles 312 and bottom needles 342 are respectively installed in the needle grooves 311 of the top needle plate 31 and the needle grooves 341 of the bottom needle plate 34. A motor 35 is installed in the suspension rack 141, and controlled to rotate the center shaft 32 through a transmission gear set 36, thereby causing the needle plate holders 3 and 33 and the needle plates 31 and 34 to be rotated with the center shaft 32. Please see also FIGS. from 15 through 19, a top cam holder 23 and a bottom cam holder 24 are respectively disposed corresponding to the top needle plate holder 3 and the bottom needle plate holder 33. Top cams 214 and bottom cams 224 are respectively fastened to respective screw holes 232 and 242 at the peripheral flanges 231 and 241 of the top cam holder 23 and the bottom cam holder 24. The top cams 214 and the bottom cams 224 each comprise a track block 2141 or 2241 defining a track 2142 or 2242 adapted to receive the butt 3121 or 3421 of the top needles 312 or bottom needles 342 respectively. When rotating the needle plates 31 and 34, the butts 3121 and 3421 of the needles 312 and 342 are respectively moved in the tracks 2141 and 2241, thereby causing the needles 312 and 342 respectively reciprocated. As indicated, the top cam holder 23 and the bottom cam holder 24 have a circular shape and screw holes 232 and 242 for the mounting of the cams 214 and 224. Normally, the number of the cams 214 and 224 can be 60, 72, 84 or 94. The number of the track blocks 2141 and 2241 is directly proportional to the number of the cams 214 and 224. The more the number of the cams 214 and 224 is, the faster the knitting speed will be. In order to fit different knitting speed requirements, different knitting machines with different numbers of cams shall be provided. For the sake of saving cost, there are provided knitting machines with replaceable cam holders. These knitting machines enable the user to replace different specifications of cam holders 23 and 24 to hold different numbers of cams 214 and 224. However, when replacing the cam holders 23 and 24, it is necessary to detach the yarn-feeding unit 13, the supports 14, and the knitting unit 2. Further, the mounting arrangement of the cams 214 and 224 according to the prior art is complicated. As illustrated in FIGS. 17 and 19, the cam holders 23 and 24 have screw holes 232 and 242 mounted with a respective locating rod 26. The cams 214 and 224 have slots 27 adapted to receive the locating rods 26 at the cam holders 23 and 24. Further, screws 2142 and 2243 are respectively obliquely installed to secure the cams 214 and 224 in place. This cam mounting arrangement has numerous drawbacks as outlined hereinafter.
1. The locating rods 26 are cylindrical members, they cannot let the central axis of the cams 214 and 224 be aimed at the same center accurately, thereby causing the cams 214 or 224 cannot be smoothly connected to one another (see FIG. 20). Unstable arrangement of the cams 214 and 224 affects the knitting quality.
2. The specifications of the cams 214 and 224 must be matched with the specifications of the cam holders 23 and 24, i.e., cam holders 23 and 24 of relatively bigger diameter must be used when the number of cams 214 and 22 are to be increased. Further, because the curvature of the alignment portions 28 of the cams 214 and 224 must fit the curvature of the alignment portion 29 of the cam holders 23 and 24, different specifications of cams 214 and 224 and different specifications of cam holders 23 and 24 must be prepared. Preparing a bit number of different specifications of cams 214 and 224 and different specifications of cam holders 23 and 24 require much storage space and investment.